Reciprocal-movement power tool

ABSTRACT

A reciprocal-movement power tool includes a movable blade reciprocally movably provided on a main body. A receiving plate that supports an angle iron to be cut is supported on the main body at a position in front of the movable blade. The movable blade is fixed on a front tip of a rod-shaped shuttle screw. The shuttle screw moves back and forth in the axial direction within a tubular screw shaft. The screw shaft is carved with a female screw portion and is rotated through a joint spindle that is deceleratingly rotated upon rotation of the motor through a deceleration means. The shuttle screw has a male screw portion that is threadingly engageable with the female screw portion.

TECHNICAL FIELD

The present invention relates to an electrically poweredreciprocal-movement tool, and more particularly to a reciprocal-movementpower tool that can be used as a cutting device, a crimp tool and acalking gun. The cutting device is adapted for cutting an angle ironsuch as light weight ceiling bars, which are steel furrings for wall andceiling in buildings. The crimp tool is adapted for crimping terminals,and the calking gun is adapted for ejecting calking material.Hereinafter, a reciprocal-movement tool will be described in the form ofa cutting device for cutting the steel furrings for wall and ceiling inbuildings.

BACKGROUND ART

In building construction, there is a light-weight steel frame ceilingmade by suspending hanging bolts from a ceiling slab, using the hangingbolt to assemble ceiling bars and ceiling bar supports into a lattice,and suspending boards on the lattice. The ceiling bars and ceiling barsupports used in this ceiling are defined by JIS in the classificationof steel furrings for wall and ceiling in buildings. The steel furringsare plate-shaped steel having a thickness of 0.5 mm that is formed bybending into a U shape. Hereinafter, the steel furrings will be referredto as an angle iron.

Conventionally, angle irons are cut to match the length of boards usinga power grinder, for example. Because the grinder is power driven, theangle iron can be cut in just a few seconds. However, grinding dust andchips may be scattered around ambient objects and sparks may fly arounddue to high speed rotation of the grinding stone.

A hand-driven tool for overcoming this problem is disclosed in JapanesePatent-Application Publication HEI-9-108931. The hand-driven toolincludes a reception plate and a movable blade. The reception plate isfor supporting the angle iron and matches the shape of the angle iron tobe cut. The movable blade is disposed in confrontation with thereception plate. The movable blade has thin and sharp blade tip, and iscapable of reciprocal movement. By manually operating a lever severaltimes, the movable blade moves toward the reception plate, so that theangle iron that is supported by the reception plate is pressingly cut byshearing force. Because the angle irons are pressingly cut by themovable blade, this device has the merit of not generating cutting dust.On the other hand, there are problems in that the user's hand can becometired because the device is manually operated and also cutting takes along time to complete.

It is conceivable to make the device into a power tool for eliminatingthe problem of the user's hand getting tired and for reducing cuttingtime. However, making the device into an electric power tool involvesthe following problems.

First, a large space is required for setting the angle iron between thereception plate and the movable blade. Because the movable blade must bemoved by the distance of the space, the time required for cutting isincreased and safety measures must be considered to prevent objects fromentering into the space while the angle iron is being cut. Also,although a great cutting force of 600 to 800 Kg is needed, it isextremely difficult to secure such a large cutting force. It isconceivable to use hydraulics but this would made the configurationcomplex and expensive.

Taking the above-described problems into account, it is an object of thepresent invention to provide an inexpensive electrically poweredreciprocal-movement power tool capable of providing a large cuttingforce using a simple configuration and without generating cutting dust.

DISCLOSURE OF THE INVENTION

In order to achieve these objects, the present invention provides areciprocal-movement power tool characterized by including a main body, amotor fixed to the main body, deceleration means disposed in the mainbody and connected to the motor, an output shaft connected to thedeceleration means and rotating in a decelerated manner, a feed screwshaft, a movement shaft, a movable body mounted on a tip end of themovement shaft, and a fixed body. The feed screw shaft is rotatablysupported on the main body and is connected to the output shaft so as torotate with the output shaft. The feed screw shaft has a first screwportion. The a movement shaft is disposed coaxially with the feed screwshaft and has a second screw portion that threadingly engages the firstscrew portion of the feed screw shaft. The movement shaft moves back andforth in an axial direction thereof by the threading movement of thesecond screw portion relative to the first screw portion. The fixed bodyis supported on a front side of the main body. The movable body movesback and forth with respect to the, fixed body by the movement of themovement shaft.

The movable body can move forward with a large load of about 600 to 800kg by the rotational advancing force of the screw. Also, the device ispower driven, not manually driven. Therefore, operations can beperformed speedily and efficiently without tiring the operator. Also,the back and forth movement of the movable body can be achieved bymerely switching the rotational direction of the screw shaft and a largeforce can be generated even during the backward movement of the movablebody.

Here, by making the fixed body a receiving plate supporting a workpieceand the movable body a movable blade having a blade portion at its frontend, the reciprocal-movement power tool can be a cutting device thatmoves the movable blade toward the receiving plate to cut the workpiecewith a shearing cut. In this case, because as described above, themovable blade can move forwardly with a large load by rotationaladvancing force of the screw, no cutting dust or sparks are generated sothe operation environment is greatly improved. Also, because a largeforce can be generated when the movable blade moves backward, themovable blade can be forcibly pulled back even if the movable bladecatches on burs and the like at the time of cutting. Consequently,operability can be improved.

In case of the cutting device, it is desirable that a holder forcovering around the movable blade be fixed to the front side of the mainbody, and that the receiving plate be attached so as to be capable ofselectively being pivoted and fixed with respect to the holder.

Accordingly, because the receiving plate is pivotably provided to theholder, and is not moved in the cutting direction as in the conventionaldevice, then if, for example, the receiving plate can be pivotedsubstantially perpendicular to the cutting direction, then a largeworking space can be opened up below the receiving plate when the angleiron is to be inserted into the receiving plate, so that operations forinserting the angle iron can be simplified. Further, when the angle ironis set in the receiving plate, the receiving plate can be disposed outof the forward movement direction of the movable blade. Therefore,safety is assured even if the movable blade moves forward.

Further, it is desirable that the feed screw shaft is in a form of ahollow tube having an inner peripheral surface sectioned into a frontnon-screw portion, an intermediate female screw portion serving as thefirst screw portion, and a rear non-screw portion. It is also desirablethat the movement shaft is in a form of a rod-shaped member disposedwithin the hollow-tube, the rod shaped member having an outer peripheralsurface sectioned into a male screw portion serving as the second screwportion, the male screw portion and the female screw portion beingscrewingly engaged at only a predetermined region, and the female screwportion being disengaged from the male screw portion at regions otherthan the predetermined region so that the feed screw shaft rotates idly.

By setting the positional relationship with respect to axial lengths ofthe male screw portion and the female screw portion so that threadingengagement between the male screw portion and the female screw portionis released when cutting is completed and when the movable blade movesback to its initial position, the feed screw portion will rotate idlyonly at such disengagement phases. Therefore, the motor will not lockeven if rotation of the motor is continued. This facilitates control tothe main switch. No complicated clutch mechanism is needed, yet aninexpensive cutting device can be provided.

Further, it is desirable that the feed screw shaft is supported movablein an axial direction with respect to the main body, and the feed screwshaft and the output shaft are connected through a groove and a pinmovably engaged with the groove, the groove extending in a slantingdirection with respect to the axial direction of the feed screw shaft,movement of the feed screw shaft in the axial direction being startedfor permitting the female screw portion to become engaged with the malescrew portion upon sliding movement of the pin along the groove when therotational direction of the output shaft is switched.

Because the groove extends at a slant with respect to the axialdirection of the feed screw shaft and the pin is engaged with thegroove, each time the rotation of the motor is reversed the pingenerates a force for moving the feed screw shaft forward or backward inthe axial direction. This causes threading engagement of the femalescrew portion with the male screw portion so that idle rotation of thefeed screw shaft is terminated to again move the movable body.

Further, by making the fixed body a die supporting a terminal to becrimped and the movable body a punch, the reciprocal-movement power toolcan be operated as a crimping device that crimps the terminal by movingthe punch toward the die.

Also, by making the fixed body a cylinder accumulating calking materialand the movable body a piston moving within the cylinder, thereciprocal-movement power tool can be operated as a calking gun thatejects out the calking material from the cylinder upon movement of thepiston.

As described above, the present invention enables a reciprocal-movementpower tool to be provided inexpensively and with a simple configuration.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings,

FIG. 1 is a side cross-sectional view showing an embodiment wherein thereciprocal-movement power tool of the present invention is applied to anangle iron cutting device,

FIG. 2 is a perspective view showing the condition of the cutting deviceof FIG. 1 before a cutting operation;

FIG. 3 is a perspective view showing a cutting operation condition ofthe cutting device of FIG. 1;

FIGS. 4(a) through 4(f) are explanatory viewing showing essentialportions for description of operation principles of the cutting deviceof FIG. 1, in which

FIG. 4(a) indicates a condition after the blade moves to the rearmostposition;

FIG. 4(b) indicates a condition when the blade starts moving forward;

FIG. 4(c) indicates a cutting condition wherein the blade is movedforward to cut an angle iron;

FIG. 4(d) indicates a condition immediately after cutting is completed;

FIG. 4(e) indicates a condition when the blade starts moving rearwardafter cutting the angle iron;

FIG. 4(f) indicates the condition of the blade moving rearward;

FIG. 5 is a side view showing a shaft screw and a joint spindle thatconfigure the cutting device of FIG. 1;

FIG. 6 is a side view showing a screw shaft that configures the cuttingdevice of FIG. 1;

FIG. 7 is a side cross-sectional view showing a second embodimentwherein the reciprocal-movement power tool of the present invention isapplied to a crimping device;

FIG. 8 is a third embodiment wherein the reciprocal movement power toolof the present invention is applied to a calking gun; and

FIG. 9 is a diagram of electric circuitry of a reciprocal-movement powertool according to the present invention for switching a motor betweenforward and reverse rotation by manipulating only a main switch, withoutproviding a push switch.

BEST MODE FOR CARRYING OUT THE INVENTION

Below an angle iron cutter according to an embodiment of the presentinvention will be described with reference to FIGS. 1 to 6. A main bodyof the cutter includes a motor chamber 1 that houses a motor 5, ahousing 3 disposed in a T-shape in combination with a handle 2, and agear cover 16. A storage battery 4 is detachably provided to the lowerportion of the handle 2. A main switch 6 and a push button 7 areprovided to the handle 2. The main switch 6 is for starting and stoppingapplication of electric current to the motor 5. The push button 7 is forswitching the polarity of voltage supplied to the motor 5 to change therotational direction of the motor 5.

The gear cover 16 is fixed to the front end of the housing 3. A holder19 is fixed to the front end of the gear cover 16. Three stage planetarygear train 8, a joint spindle 9, a pin 10, a screw shaft 11, and ashuttle screw 12 are provided within the housing 3 and the gear cover16. The joint spindle 9 configures an output shaft of the presentinvention. The screw shaft 11 configures a feed screw shaft of thepresent invention. The shuttle screw 12 configures a movement shaft ofthe present invention. Also, a movable blade 13 is movably disposed inthe holder 19. The three stage planetary gear train 8 connected to thejoint spindle 9 is for decelerating rotation of the motor 5 by about1/100. As will be described later, the joint spindle 9 is connected tothe screw shaft 11 by the pin 10. The shuttle screw 12 is selectivelyconnected to the screw shaft 11. The movable blade 13 is fixed to thefront end of the shuttle screw 12.

As shown in FIG. 5, a flange 9A is provided on the rear end of the jointspindle 9. The pin 10 is force-fitted with the front end portion of thejoint spindle 9 in the radial direction of the joint spindle 9 and fixedin place there so as to protrude radially outwardly.

The screw shaft 11 has a hollow cylindrical configuration including arear small-diameter sleeve portion 11 a, a front large-diameter sleeveportion 11 b, and a front-end flange portion 11 c. The rearsmall-diameter sleeve portion 11 a is loosely fitted to the outerperiphery of the joint spindle 9. The rear end face of the screw shaft11 is disposed capable of abutment with and separation from the flange9A of the joint spindle 9. The screw shaft 11 is rotatably supported inthe gear cover 16 through metal bearings 14, 15 at two positions, oneforward and one rearward. A thrust needle bearing 17 is provided betweenthe flange portion 11 c of the screw shaft 11 and the metal bearing 14.The front portion of the screw shaft 11 is thus supported by thrustneedle bearing 17 so as to be movable with respect to the gear cover 16in the axial direction within a predetermined range.

A right-handed female screw portion 11 d is engraved into the innerperipheral surface at the front side of the front large-diameterportion. The cross-section of the female screw 11 d has a trapezoidalshape. The inner peripheral surface of the large-diameter portion 11 bbetween the female screw 11 d and the rear small-diameter sleeve portion11 a forms a non-screw portion lie with an inner diameter that is largerthan that of the female screw portion 11 d. It should be noted that nomale screw portion is carved in the inner peripheral surface of thefront-end flange portion 11 c. Two slots 11 f are formed at 180 degreesymmetrical positions in the rear small-diameter sleeve portion 11 a.The slots 11 f are slanted at an approximately 45 degree angle withrespect to the axial direction of the screw shaft 11. The slantdirection of the slots 11 f is a leftward slant (FIG. 4). Saiddifferently, when viewed from the right-hand rotational directioncentered on the axial center of the screw shaft 11, the slots 11 f areslanted so that the rotational direction tip sides of the slots 11 f arecloser to the rear end of the screw shaft 11 and the rotationaldirection rear sides of the slots 11 f are closer to the front of thescrew shaft. It should be noted that if the female screw portion 11 d isa left-hand screw, then the slanting direction of the slots 11 f shouldbe a rightward slant. The pin 10 that protrudes from the joint spindle 9slidingly engages in the slots 11 f. The rotation of the joint spindle 9is transmitted to the screw shaft 11 through the pin 10.

The shuttle screw 12 is axially movable in the screw shaft 11 coaxiallytherewith. The shuttle screw 12 is configured integral from a rear sidecylindrical shaft portion 12 a, a male screw portion 12 b, and a frontside cylindrical shaft portion 12 c. The male screw portion 12 b has atrapezoidal shaped male screw, and is positioned between the cylindricalshaft portions 12 a and 12 c, and is threadingly engageable with thefemale screw portion 11 d of the screw shaft 11. The axial lengths ofthe front side cylindrical shaft portion 12 c, the rear side cylindricalshaft portion 12 a, the male screw portion 12 b, the female screwportion 11 d, and the non-screw portion 11 e are set so that the screwshaft 11 can idly rotate when the male screw portion 12 b is disengagedfrom the female screw portion 11 d of the screw shaft 11 while theshuttle screw 12 is in its most retracted position providing a retractedposition of the movable blade 13, and so that the screw shaft 11 canidly rotate when the male screw portion 12 b is disengaged from thefemale screw portion 11 d of the screw shaft 11 while the shuttle screw12 is in its forward-most position providing a forward position of themovable blade 13.

The movable blade 13 is a keen blade with edge thickness of about 1.2mm. The movable blade 13 is fixed to the blade holder 18 by two screwsnot shown in the drawings. The blade holder 18 is fixed to the front ofthe shuttle screw 12 and is supported so as to be reciprocally movablewithin the holder 19 following guide grooves not shown in the drawingsformed in the holder 19. A latch engagement portion 19 a is formed inthe side portion of the holder 19.

A receiving plate 20 is supported to the holder 19 in the front-side inthe forward movement direction of the movable blade 13. As shown in FIG.1, the receiving plate 20 is provided with a total of four grooves 20 a,20 b, a pair of grooves 20 a in which a narrow-width angle iron isfitted and a pair of grooves 20 b in which a broad-width angle iron isfitted. As shown in FIG. 2, the receiving plate 20 has a pair ofreceiving plate members 20A, 20B that mutually confront each other. Aspace 20C is provided in between the receiving plate members 20A and 20Bso as to enable the blade holder 18 to pass therethrough.

One end of the receiving plate 20 is pivotably supported on the holder19 about a pivot shaft 21. A latch 23 is attached to a free end of thereceiving plate 20. The latch 23 is engageable with the latch engagementportion 19 a of the holder 19. A lever 23 a is provided on the latch 23.The lever 23 a is connected to a spring 22 and is urged to pivot in apredetermined direction. Accordingly, the receiving plate 20 ispivotable between an open condition (FIG. 2) open 90 degree centered onthe shaft 21 and a closed condition (FIG. 3) wherein the receiving plate20 is parallel with the holder 19. When in the closed condition, thelatch 23 catches on the latch engagement portion 19 a of the holder 19so that the receiving plate 20 can be prevented from opening. Also, bypressing the lever 23 a of the latch 23 against urging force of thespring 22, the latch 23 is disengaged from the latch engagement portionso that the receiving plate 20 can switch into its open condition. Whenthe receiving plate 20 is in the closed condition, a gap δ1 between themovable blade 13 and the receiving plate 20 is 8 mm or less even whenthe movable blade 13 is in the most retracted position. The gap δ1 isset to a dimension so that fingers and the like cannot entertherethrough. When the receiving plate 20 is in the closed condition, agap δ2 between the front-end opening edge of the holder 19 and thereceiving plate 20 is also 8 mm or less. A microswitch 24 is provided onthe opposite side of the lever 23 a with respect to the latch 23. Themicroswitch 24 is connected in series with the main switch 6. Themicroswitch 24 is pressed by the latch 23 and is turned ON when thelatch 23 is engaged with the latch engagement portion 19 a, and isturned OFF when the latch 23 is moved away from the microswitch 24. Themotor 5 will not rotate as long as the microswitch 24 is not turned ONregardless of the manipulation of the main switch 6.

Next, the operations of the above-described angle iron cutter will bedescribed.

As shown in FIG. 2, the receiving plate 20 is opened about the pivotshaft 21 to 90 degrees with respect to the movable blade 13. At thistime, a space sufficient for enabling the angle iron 30 to be cut topass through is opened below the receiving plate 20. Because themicroswitch 24 is in an OFF condition, the motor 5 will not rotate evenif the main switch 6 is erroneously manipulated. On the other hand, evenif the motor 5 accidentally rotates so that the movable blade 13 movesforward, there is no danger that objects, such as hands, will be cuteven if the objects are located in front of the movable blade 13 becausethe receiving plate 20 is not in front of the movable blade 13.

Next, the angle iron 30 is set in the grooves 20 a or the grooves 20 bof the receiving plate 20 and the main body is rotated 90 degree to letthe movable blade 13 direct in parallel with the receiving plate 20. Asa result, as shown in FIG. 3 the latch 23 catches on and is held in thelatch engagement portion 19A of the holder 19. At this time, because thelatch 23 is urged by the spring 22, the latch 23 will not separate fromthe latch engagement portion 19 a and the receiving plate 20 will notopen up. The microswitch 24 provided on the holder 19 is pressed by thelatch 23 into ON condition so that the motor 5 can be rotated bymanipulation of the main switch 6. Because the gap δ1 between thereceiving plate 20 and the movable blade 13 is set to 8 mm or less asdescribed above, there is no danger that objects, such as fingers, willenter.

When the main switch 6 is manipulated, the motor 5 rotates at 20,000R.P.M. This rotation is decelerated by the three-stage planetary geartrain 8 to about 1/100. Rotation of the three-stage planetary gear train8 is transmitted to the joint spindle 9 and the screw shaft 11 rotatesleftward by engagement between the pin 10 and the slots 11 f. It shouldbe noted that the pin 10 is maintained in a condition in abutmentagainst the left end portion (front-side end portion) of the slots 11 f.

FIG. 4(c) shows cutting phase upon frontward movement of the blade forcutting the angle iron. In this condition, because the female screwportion 11 d of the screw shaft 11 and the male screw portion 12 b ofthe shuttle screw 12 are in screwing engagement, leftward rotation ofthe screw shaft 11 presses the movable blade 13, which is connected tothe shuttle screw 12, forward by a force of 600 to 800 kg. The movableblade 13 cuts into and severs the angle iron 30. Because the movableblade 13 is sharp and moves slowly, no sparks will be emitted. Also,because it is a shearing cut, no cutting dust will be generated.

FIG. 4(d) shows the condition after the movable blade 13 is movedforward about 40 mm and cutting is complete. In this condition, the malescrew portion 12 b of the shuttle screw 12 is disengaged from the femalescrew portion 11 d of the screw shaft 11 and the rear side cylindricalshaft portion 12 a is positioned within the female screw portion 11 d.Therefore, even if leftward rotation of the screw shaft 11 continues,the screw shaft 11 will merely rotate idly and the shuttle screw 12 willnot move forward. Because of this, even if the operator pulls the mainswitch 6 after cutting is complete, the motor 5 will not lock up.

Next, the return operation of the movable blade 13 will be described.When the push button 7 is pressed and polarity of voltage applied to themotor 5 is reversed, and then the main switch 6 is pulled, direction ofcurrent flowing into the motor 5 reverses so that the motor 5 rotates inthe opposite direction. Accordingly, the joint spindle 9 rotates inreverse to the right. The male screw portion 12 b of the shuttle screw12 is not screwingly engaged with the female screw portion 11 d of thescrew shaft 11. Therefore, even if the screw shaft 11 rotates rightward,the screw shaft 11 will only rotate idly. However, because the pin 10 ofthe joint spindle 9 is slidingly engaged in the slots 11 f, which slantat 45 degree angles, the rightward rotation of the joint spindle 9causes sliding movement of the pin 10 from the front-side end portion tothe rear-side end portion of the slots 11 f. As a result of thisoperation, the screw shaft 11 is subjected to a forward pressing forceFm as shown in FIG. 4(e). By this pressing force, rightward rotation ofthe screw shaft 11 starts to threadingly engage the female screw portion11 d of the screw shaft 11 with the male screw portion 12 b of theshuttle screw 12 and, as shown in FIG. 4(f), the shuttle screw 12 isforcedly pulled into the screw shaft 11 and the movable blade 13retracts. The returning force of the shuttle screw 12 generated at thistime is sufficiently strong because of the axial moving force isprovided by the screw engagement. Therefore, the movable blade 13 can beforcibly returned back even if there is a large friction force due todeep thrusting of the movable blade 13 into the severed angle iron 30.

When the movable blade 13 has completed retracting back by about 40 mm,then as shown in FIG. 4(a), the male screw portion 12 b of the shuttlescrew 12 is disengaged from the female screw portion 11 d of the screwshaft 11 and the front side cylindrical shaft portion 12 c of theshuttle screw 12 is positioned within the female screw portion 11 d. Inthis condition, the screw shaft 11 will merely rotate idly and theshuttle screw 12 will not retract even if the screw shaft 11 continuesto rotate to the right. By this, there is no danger that the motor 5will lock up even if the operator pulls on the main switch 6 after themovable blade 13 has returned.

The-latch 23 is removed from the latch engagement portion 19 a bypressing the lever 23 a. By pivoting the receiving plate 20 by 90degrees, the lower side of the receiving plate 20 is opened up and theangle iron 30 can be removed. Because the microswitch 24 is turned OFFat this time, the motor 5 will not rotate even if the main switch 6 iserroneously operated. Therefore, the device is safe. Even if the motor 5rotates for some reason and the movable blade 13 moves forward, thereceiving plate 20 still remains at a positional relationship shifted by90 degrees relative to the movable blade 13. Therefore, there is nodanger of objects being interposed between the movable blade 13 and thereceiving plate 20.

Next, when another angle iron 30 is to be cut, the new angle iron 30 isset in this condition, the tool body is rotated 90 degrees, and thereceiving plate 20 is closed following the process described above. Whenthe push button 7 is pressed to the forward rotation side to switchrotational direction of the motor 5 to forward rotation and the mainswitch 6 is turned ON, then the motor 5 rotates forward. Accordingly,the joint spindle 9 rotates leftward. As described above, because themale screw portion 12 b of the shuttle screw 12 is disengaged from thefemale screw portion 11 d of the screw shaft 11, the screw shaft 11 willonly rotate idly even if the screw shaft 11 rotates to the left.However, because the pin 10 of the joint spindle 9 is slidingly engagedwith the slots 11 f, which slant at 45 degree angles, leftward rotationof the joint spindle 9 causes sliding movement of the pin 10 from therear-side end portion of the slots 11 f to the front-side end portionthereof. As indicated in FIG. 4(b), a rearward pressing force Fh isgenerated on the screw shaft 11 during this sliding movement of the pin.As a result, leftward rotation of the screw shaft 11 starts to provideengagement of the female screw portion 11 d of the screw shaft 11 withthe male screw portion 12 b of the shuttle screw 12. Thus, as shown inFIG. 4(c), the shuttle screw 12 is forcibly pressed out and the movableblade 13 cuts the angle iron 30.

The above-described angle iron cutter achieves the following effects:

(1) The receiving plate 20 supports the angle iron 30 to be cut. Also,the thin movable blade 13 is reciprocally moved and pressingly cuts by alarge pressing force generated by axially advancing rotation force of ascrew. Therefore, no cutting dust or sparks are generated so theoperation environment is greatly improved.

(2) The movable blade 13 moves reciprocally by a large load of 600 to800 Kg. However, this is power driven, not manually driven. Therefore,cutting can be much more speedily and efficiently performed without theoperator tiring.

(3) The receiving plate 20 is pivoted about the shaft 21 in a directionthat is substantially perpendicular to the cutting direction, not in thecutting direction in the manner of the conventional device. Thereceiving plate 20 and the movable blade 13 are shifted by 90 degreeswhen the angle iron 30 is inserted. Therefore, a large working space isopened below the receiving plate 20 so that the angle iron 30 can beeasily set. Also, after the tool body is rotated by 90 degrees to bringthe receiving plate 20 and movable blade 13 into a parallelrelationship, the gap 61 between receiving plate 20 and the movableblade 13 or the gap 62 between the receiving plate 20 and the holder 19is narrow such as 8 mm or less. Thus safety increases because there isno large space at the gap, thereby eliminating or reducing possibilityof insertion of objects into the gap.

(4) The motor 5 rotates the screw shaft 11, which is carved with thefemale screw portion 11 d, and the movable blade 13 is pressed throughthe shuttle screw 12, which has the male screw portion 12 b in screwingengagement with the female screw portion 11 d. Therefore, a largecutting force can be generated from a small rotational force.

(5) Moving direction of the movable blade 13 can be changed by merelyswitching rotational direction of the screw shaft 11, and a large forcecan be generated during return stroke of the movable blade 13.Therefore, the movable blade 13 can be forcibly returned even if themovable blade 13 gets stuck on burs and the like generated duringcutting, so that operability can be enhanced.

(6) By properly setting dimensional relationship between the male screwportion 12 b and the female screw portion 11 d, screwing engagementbetween the female screw portion 11 d and the male screw portion 12 bcan be released when cutting is completed and when the movable blade 13returns to its initial position, so the screw shaft 11 can idly rotate.Therefore, the motor 5 will not lock up even if the motor 5 continues torotate. Also, control to the main switch 6 is also simple and there isno need for a complicated clutch mechanism. Thus, resultant cuttingdevice can be inexpensively provided.

(7) The approximately 45 degree angle slots 11 f are formed in the screwshaft 11, and the pin 10 protruding from the joint spindle 9 is engagedwith the slots 11 f. Therefore, forward movement and retracting forcesFm and Fh are generated in the axial direction by rotating the jointspindle 9 forwardly and reversely. Because the direction of thrust forcein the rotational direction matches the screw engagement direction, theforce Fm is generated that threadingly engages the female screw portion11 d with the male screw portion 12 b when forward rotation is shiftedto reverse rotation. The screw portions can be smoothly threadinglyengaged by this reverse rotation. Also, when the rotating direction ischanged from the reverse rotation to the forward rotation at the time ofidle rotation of the screw shaft 11, the force Fh is generated thatthreadingly engages the male screw portion 12 b with the female screwportion 11 d. Therefore, through the forward rotation, the screwportions can be smoothly threadingly engaged with each other.

(8) The angle iron 30 is set after the receiving plate 20 is pivoted 90degrees. Therefore, the receiving plate 20 can be positioned so that itis not in front of the movable blade 13 when the angle iron is set. Itwill be safe even if the movable blade 13 moves forward. Also, in thiscondition the microswitch 24 is in an OFF condition. Therefore, themovable blade 13 will not move even if the main switch 6 is erroneouslyoperated, so safety device results.

FIG. 7 shows a second embodiment wherein the present invention isapplied to a crimping device. In FIG. 7, like parts and components aredesignated by the same reference numerals as those shown in FIGS. 1through 6. Instead of the movable blade 13 of the first embodiment, apunch 40 is connected to the shuttle screw 12. Instead of the receivingplate 20 of the first embodiment, a die 41, in which a terminal 42 canbe mounted, is pivotably supported on the holder 19. The terminal 42 canbe crimped by pressing the punch 40 against the terminal 42 supported inthe die 41.

FIG. 8 shows a third embodiment that applies the present invention to acaulking gun. The movable blade 13 and the receiving plate 20 of thefirst embodiment are replaced by a piston 50 and a cylinder 51,respectively. By moving the piston 50 forward, caulking agent filled inthe cylinder 51 can be ejected out from a nozzle 53 at the front end ofthe cylinder.

In the above-described first to third embodiments, the rotationaldirection of the motor 5 is changed by manipulating the push button 7.However, by using a circuit configuration shown in FIG. 9, the pushbutton 7 can be dispensed with. By merely manipulating the main switch6, rotational direction of the motor 5 can be switched and a series ofoperations can be performed. In the motor power supply circuit shown inFIG. 9, the power source 4, the motor 5, a resistor 63, and the mainswitch 6 are serially connected. The resistor 63 is connected at one endto ground and at the other end to an inverting terminal of an amplifier64 through a resistor. A non-inverting terminal of the amplifier 64 isgrounded. The amplifier 64 is connected to a microcomputer 62. Athree-terminal regulator 60, one end of which is connected to ground,and a smoothening capacitor 61 are connected to the microcomputer 62 forsupplying a rated voltage to the microcomputer 62. The microcomputer 62includes an A/D input port and an output port. The A/D input portreceives input of voltage from the amplifier 64. The output portincludes a first output terminal 62A and a second output terminal 62B.The first output terminal 62A is connected to a first transistor 65through a resistor. The first transistor 65 is connected to a firstrelay coil 67, which is in parallel with the motor 5. The second outputterminal 62B is connected to a second transistor 66 through a resistor.The second transistor 66 is connected to a second relay coil 68 which isin parallel with the motor 5. A pair of motor-forward-rotation contacts67 a, 67 a are operatively associated with the first relay coil 67. Thecontacts 67 a, 67 a are disposed in series to the front and rear of themotor 5. A pair of motor-reverse-rotation contacts 68 a, 68 a areoperatively associated with the second relay coil 68. The contacts 68 a,68 a are disposed in series to the front and rear of the motor 5. Uponenergization of the first relay coil 67 by turning ON the firsttransistor 65, the motor-forward-rotation contacts 67 a, 67 a are closedwhile the open condition of the motor-reverse-rotation contacts 68 a, 68a is maintained. As a result, electric current flows in one direction inthe motor 5. On the other hand, upon energization of the second relaycoil 68 by turning ON the second transistor 66, themotor-reverse-rotation contacts 68 a, 68 a are closed while the opencondition of the motor-forward-rotation contacts 67 a, 67 a ismaintained. As a result, electric current flows in the oppositedirection in the motor 5.

The microcomputer 62 is configured to (a) output a high-level signalfrom the first output terminal 62A and a low-level signal from thesecond output terminal 62B upon detection of turning ON the main switch6 (b) to output a low-level signal from the first output terminal 62Aand a high-level signal from the second output terminal 62B by input ofa DC current, whose level is lower than a predetermined current level,from the amplifier 64 according to a rapid reduction on the motor loadas a result of idle rotation of the screw shaft 11 at the completion ofcutting (c) and to output a low-level from the first output terminal 62Aand from the second output terminal 62B in response to the second inputof a DC current whose current level is lower than the predeterminedcurrent level according to the disengagement of the screw shaft 11 at aterminal phase of the return stroke of the movable blade 13.

With the above-described configuration, when the microcomputer 62detects that the main switch 6 is turned ON, the high-level signal isoutput from the first output terminal 62A and the low-level signal isoutput from the second output terminal 62B. Thus, the first transistor65 is rendered ON, so that the first relay coil 67 is energized forclosing the contacts 67 a. Therefore, the motor 5 is rotated forward. Asdescribed above, as a result the shuttle screw 12 moves forward and themovable blade 13 cuts the angle iron 30.

Because the screw shaft 11 rotates idly when cutting is completed, asmaller current flows in the motor 5. The microcomputer 62 receives anoutput of the predetermined current value or less from the amplifier 64,and judges that the load on the motor 5 is smaller, and outputs alow-level signal from the first output terminal 62A, and outputs ahigh-level signal from the second output terminal 62B. Consequently, thefirst transistor 65 is rendered OFF for opening the contacts 67 a,whereas the second transistor 66 is rendered ON, so that the secondrelay coil 68 is energized for closing the contacts 68 a. As a result,reverse rotation of the motor 5 starts and the shuttle screw 12retracts.

When the shuttle screw 12 retracts by a predetermined distance, thescrew shaft 11 again rotates idly in the manner described above. Themicrocomputer 62 receives the second low current output level from theamplifier 64, judges that the load on the motor 5 has again becomesmall, and outputs a low-level signal from the first output terminal 62Aand the second output terminal 62B. As a result, the second transistor66 is also rendered OFF and the motor 5 stops. This completes a seriesof operations.

Incidentally, a non-volatile memory (not shown) can be provided in theabove circuit. When the main switch is turned OFF for temporarilystopping cutting operation, the condition of the microcomputer at thestopping phase thereof can be held in the non-volatile memory. When themain switch is again turned ON, operations restart from the time thatthe microcomputer was stopped and cutting operations continue fromthere. Alternatively, the number of times that current drops asdescribed above can be counted, and idle rotation timing of the screwshaft 11 can be determined upon set or reset condition of flags, thedetermination being, made as to whether the screw shaft 11 is idlyrotating at the immediate end timing of a cutting operation or whetherthe screw shaft 11 is idly rotating after the shuttle screw 12 moves toits retracting end.

With this configuration, cutting can be performed by merely maintainingthe ON condition of the main switch 6. Therefore, there is no need tomanipulate the push button 7 or to manipulate the main switch 6 at thetime of reverse rotation. Thus, operability can be enhanced. Also,simple arrangement results because of elimination of the push button 7.

It should be noted that the reciprocating power tool according to thepresent invention is not limited to the above-described embodiments andcan be modified in a variety of ways within the scope of the claims. Forexample, in the embodiments, the slanting slots 11 f are formed in thetubular shaped screw shaft 11 and a pin 10 is provided in the jointspindle 9 for engagement with the slots 11 f. However, a pin can beprovided integrally to the screw shaft and a slanting groove thatengages with the pin can be formed in the joint spindle. Also, the slots11 f are formed so as to penetrate through the tube wall of the screwshaft 11. However, grooves can be used instead of slots.

INDUSTRIAL APPLICABILITY

The electrically powered reciprocal tool according to the presentinvention can be applied to a broad range of mechanisms that moves amovable body back and forth with respect to a fixed body, such as apower cutting tool for cutting angle irons, a crimping tool for crimpingterminals, and a calking gun for ejecting calking material.

1. A reciprocal-movement power tool comprising: a main body; a motorfixed to the main body; deceleration means disposed in the main body andconnected to the motor; an output shaft connected to the decelerationmeans and rotating in a decelerated manner; a feed screw shaft rotatablysupported on the main body and connected to the output shaft so as torotate with the output shaft, the feed screw shaft having a first screwportion; a movement shaft disposed coaxially with the feed screw shaftand having a second screw portion threadingly engageable with the firstscrew portion of the feed screw shaft, the movement shaft moving backand forth in an axial direction thereof by the threading movement of thesecond screw portion relative to the first screw portion, the feed screwshaft also having a non-screw portion so that the feed screw shaft iscapable of idle rotation when it is disengaged from the movement shaftwhile being disposed coaxially therewith; a movable body mounted on atip end of the movement shaft; and, a fixed body supported on a frontside of the main body, the output shaft, the feed screw shaft, and themovement shaft being provided coaxially with one another, and themovable body moving back and forth with respect to the fixed body by themovement of the movement shaft; and further comprising a pin protrudingfrom the output shaft, and wherein the feed screw shaft is formed with aslot slanted with respect to the axial direction of the screw shaft, thepin slidingly engaging and extending through the slot.
 2. Thereciprocal-movement power tool as claimed in claim 1, wherein the fixedbody comprises a receiving plate supporting a workpiece, and the movablebody comprises a movable blade having a blade portion at its front end,the movable blade being movable toward the receiving plate to cut aworkpiece with a shearing cut.
 3. The reciprocal-movement power tool asclaimed in claim 2, further comprising a holder fixed to the front sideof the tool body for covering around the movable blade, the receivingplate being supported to the holder and being selectively movable withrespect to or selectively fixed to the holder.
 4. Thereciprocal-movement power tool as claimed in claim 1, wherein the fixedbody comprises a die supporting a terminal to be crimped, and themovable body comprises a punch movable toward the die for crimping theterminal.
 5. The reciprocal-movement power tool as claimed in claim 1,wherein the fixed body comprises a cylinder accumulating calkingmaterial, and the movable body comprises a piston moving within thecylinder for ejecting out the calking material from the cylinder.
 6. Areciprocal-movement power tool comprising: a main body; a motor fixed tothe main body; deceleration means disposed in the main body andconnected to the motor; an output shaft connected to the decelerationmeans and rotating in a decelerated manner; a feed screw shaft rotatablysupported on the main body and connected to the output shaft so as torotate with the output shaft, the feed screw shaft having a first screwportion; a movement shaft disposed coaxially with the feed screw shaftand having a second screw portion threadingly engageable with the firstscrew portion of the feed screw shaft, the movement shaft moving backand forth in an axial direction thereof by the threading movement of thesecond screw portion relative to the first screw portion; a movable bodymounted on a tip end of the movement shaft; and, a fixed body supportedon a front side of the main body, the movable body moving back and forthwith respect to the fixed body by the movement of the movement shaft;and wherein the feed screw shaft is in a form of a hollow tube having aninner peripheral surface sectioned into a front non-screw portion, anintermediate female screw portion serving as the first screw portion,and a rear non-screw portion, wherein the movement shaft is in a form ofa rod-shaped member disposed within the hollow-tube, the rod shapedmember having an outer peripheral surface provided with a male screwportion serving as the second screw portion, the male screw portion andthe female screw portion being screwingly engaged at only apredetermined region, and the female screw portion being disengaged fromThe male screw portion at regions other than the predetermined region sothat the feed screw shaft rotates idly, and wherein the feed screw shaftis supported movable in an axial direction with respect to the mainbody, and the feed screw shaft and the output shaft are connectedthrough a groove and a pin movably engaged with the groove, the grooveextending in a slanting direction with respect to the axial direction ofthe feed screw shaft, movement of the feed screw shaft in the axialdirection being started for permitting the female screw portion tobecome engaged with the male screw portion upon sliding movement of thepin along the groove when the rotational direction of the output shaftis switched.
 7. A reciprocal-movement power tool comprising: a mainbody; a motor fixed to the main body; deceleration means disposed in themain body and connected to the motor; an output shaft connected to thedeceleration means and rotatable in a decelerated manner; a feed screwshaft rotatably supported on the main body and connected to the outputshaft so as to rotate with the output shaft, the feed screw shaft havingan intermediate portion provided with a first screw portion andremaining portion provided with a non-screw portion; a movement shaftdisposed coaxially with the feed screw shaft and having one end portionprovided with a non-screw portion, an intermediate portion provided witha second screw portion threadingly engageable with the first screwportion of the feed screw shaft, and another end portion provided with anon-screw portion, the movement shaft moving back and forth in an axialdirection thereof by the threading movement of the second screw portionrelative to the first screw portion; a movable body mounted on a tip endof the movement shaft; a fixed body supported on a front side of themain body, the movable body moving back and forth with respect to thefixed body by the movement of the movement shaft, idle rotation of themotor occurring when the second screw portion disengages from the firstscrew portion; rotational direction changing means for changingrotational direction of the motor by changing a direction of currentsupplied to the motor; detection means detecting a current level flowingthrough the motor for detecting idle rotation of the motor; and, controlmeans for changing rotational direction of the motor via the rotationaldirection changing means when the detection means detects idle rotationa first time and stopping rotation of the motor when the detection meansdetects idle rotation a second time.